I have a desktop which has more than 16GB of memory that I want to dedicate as an SFTP server. Many people have suggested that I install Linux, so I have decided to go with Linux. I am puzzled and unable to judge which distribution to install. I have no ideas or exposure to Linux before. Are there any suggestions to help me meet my requirement?
If you expect this SFTP server to be long-lived, pick a "long term support" version for a distro. Many of the popular desktop distros (e.g., Fedora, most Ubuntu) stop receiving updates after a relatively short amount of time (e.g., a bit over a year after initial release).
So, the big "long term support" distros are the Red Hat Enterprise Linux-derived CentOS which tends to be more server/enterprise focused, and Ubuntu LTS, which, happily, coincides with the current Ubuntu release, version 12.04 (codenamed Precise Pangolin). Much as I live CentOS, Ubuntu is probably a bit friendlier to new users, and has extensive community support and various forums.